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<!-- Ported from the OpenGL Samples Pack https://github.com/g-truc/ogl-samples/blob/master/tests/gl-320-texture-3d.cpp -->
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<head>
    <title>WebGL 2 Samples - texture_3d</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <script src="utility.js"></script>
    <script src="third-party/gl-matrix-min.js"></script>
    <script src="third-party/noise3D.js"></script>
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<body>
    <div id="info">WebGL 2 Samples - texture_3d</div>
    <p id="description">
        This sample demonstrates creating a custom 3D texture from simplex noise.
    </p>
    <!-- WebGL 2 shaders.
        This section is adapted from Example 6.15 and 6.16,
        OpenGL® Programming Guide: The Official Guide to Learning OpenGL®, Version 4.3,
        Dave Shreiner, Graham Sellers
     -->
    <script id="vs" type="x-shader/x-vertex">
        #version 300 es
        #define POSITION_LOCATION 0
        #define TEXCOORD_LOCATION 1

        precision highp float;
        precision highp int;

        layout(location = POSITION_LOCATION) in vec2 position;
        layout(location = TEXCOORD_LOCATION) in vec2 in_texcoord;

        // Output 3D texture coordinate after transformation
        out vec3 v_texcoord;

        // Matrix to transform the texture coordinates into 3D space
        uniform mat4 orientation;

        void main()
        {
            // Multiply the texture coordinate by the transformation
            // matrix to place it into 3D space
            v_texcoord = (orientation * vec4(in_texcoord - vec2(0.5, 0.5), 0.5, 1.0)).stp;
            gl_Position = vec4(position, 0.0, 1.0);
        }

    </script>

    <script id="fs" type="x-shader/x-fragment">
        #version 300 es

        precision highp float;
        precision highp int;
        precision highp sampler3D;

        uniform sampler3D diffuse;

        in vec3 v_texcoord;

        out vec4 color;

        void main()
        {
            color = texture(diffuse, v_texcoord);
        }
    </script>

    <script>
    (function() {
        'use strict';

        var canvas = document.createElement('canvas');
        canvas.width = Math.min(window.innerWidth, window.innerHeight);
        canvas.height = canvas.width;
        document.body.appendChild(canvas);

        var gl = canvas.getContext( 'webgl2', { antialias: false } );
        var isWebGL2 = !!gl;
        if(!isWebGL2) {
            document.getElementById('info').innerHTML = 'WebGL 2 is not available.  See <a href="https://www.khronos.org/webgl/wiki/Getting_a_WebGL_Implementation">How to get a WebGL 2 implementation</a>';
            return;
        }

        // -- Divide viewport

        var windowSize = {
            x: canvas.width,
            y: canvas.height
        };

        var Corners = {
            TOP_LEFT: 0,
            TOP_RIGHT: 1,
            BOTTOM_RIGHT: 2,
            BOTTOM_LEFT: 3,
            MAX: 4
        };

        var viewport = new Array(Corners.MAX);

        viewport[Corners.BOTTOM_LEFT] = {
            x: 0,
            y: 0,
            z: windowSize.x / 2,
            w: windowSize.y / 2
        };

        viewport[Corners.BOTTOM_RIGHT] = {
            x: windowSize.x / 2,
            y: 0,
            z: windowSize.x / 2,
            w: windowSize.y / 2
        };

        viewport[Corners.TOP_RIGHT] = {
            x: windowSize.x / 2,
            y: windowSize.y / 2,
            z: windowSize.x / 2,
            w: windowSize.y / 2
        };

        viewport[Corners.TOP_LEFT] = {
            x: 0,
            y: windowSize.y / 2,
            z: windowSize.x / 2,
            w: windowSize.y / 2
        };

        // -- Initialize texture
        
        // Note By @kenrussel: The sample was changed from R32F to R8 for best portability. 
        // not all devices can render to floating-point textures 
        // (and, further, this functionality is in a WebGL extension: EXT_color_buffer_float), 
        // and renderability is a requirement for generating mipmaps.
        
        var SIZE = 32;
        var data = new Uint8Array(SIZE * SIZE * SIZE);
        for (var k = 0; k < SIZE; ++k) {
            for (var j = 0; j < SIZE; ++j) {
                for (var i = 0; i < SIZE; ++i) {
                    data[i + j * SIZE + k * SIZE * SIZE] = snoise([i, j, k]) * 256;
                }
            }
        }

        var texture = gl.createTexture();
        gl.activeTexture(gl.TEXTURE0);
        gl.bindTexture(gl.TEXTURE_3D, texture);
        gl.texParameteri(gl.TEXTURE_3D, gl.TEXTURE_BASE_LEVEL, 0);
        gl.texParameteri(gl.TEXTURE_3D, gl.TEXTURE_MAX_LEVEL, Math.log2(SIZE));
        gl.texParameteri(gl.TEXTURE_3D, gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_LINEAR);
        gl.texParameteri(gl.TEXTURE_3D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);

        gl.texImage3D(
            gl.TEXTURE_3D,  // target
            0,              // level
            gl.R8,        // internalformat
            SIZE,           // width
            SIZE,           // height
            SIZE,           // depth
            0,              // border
            gl.RED,         // format
            gl.UNSIGNED_BYTE,       // type
            data            // pixel
            );

        gl.generateMipmap(gl.TEXTURE_3D);

        // -- Initialize program
        var program = createProgram(gl, getShaderSource('vs'), getShaderSource('fs'));

        var uniformTextureMatrixLocation = gl.getUniformLocation(program, 'orientation');
        var uniformDiffuseLocation = gl.getUniformLocation(program, 'diffuse');

        // -- Initialize buffer
        var positions = new Float32Array([
            -1.0, -1.0,
             1.0, -1.0,
             1.0,  1.0,
             1.0,  1.0,
            -1.0,  1.0,
            -1.0, -1.0
        ]);
        var vertexPosBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, vertexPosBuffer);
        gl.bufferData(gl.ARRAY_BUFFER, positions, gl.STATIC_DRAW);
        gl.bindBuffer(gl.ARRAY_BUFFER, null);

        var texCoords = new Float32Array([
            0.0, 1.0,
            1.0, 1.0,
            1.0, 0.0,
            1.0, 0.0,
            0.0, 0.0,
            0.0, 1.0
        ]);
        var vertexTexBuffer = gl.createBuffer();
        gl.bindBuffer(gl.ARRAY_BUFFER, vertexTexBuffer);
        gl.bufferData(gl.ARRAY_BUFFER, texCoords, gl.STATIC_DRAW);
        gl.bindBuffer(gl.ARRAY_BUFFER, null);

        // -- Initilize vertex array

        var vertexArray = gl.createVertexArray();
        gl.bindVertexArray(vertexArray);

        var vertexPosLocation = 0; // set with GLSL layout qualifier
        gl.enableVertexAttribArray(vertexPosLocation);
        gl.bindBuffer(gl.ARRAY_BUFFER, vertexPosBuffer);
        gl.vertexAttribPointer(vertexPosLocation, 2, gl.FLOAT, false, 0, 0);
        gl.bindBuffer(gl.ARRAY_BUFFER, null);

        var vertexTexLocation = 1; // set with GLSL layout qualifier
        gl.enableVertexAttribArray(vertexTexLocation);
        gl.bindBuffer(gl.ARRAY_BUFFER, vertexTexBuffer);
        gl.vertexAttribPointer(vertexTexLocation, 2, gl.FLOAT, false, 0, 0);
        gl.bindBuffer(gl.ARRAY_BUFFER, null);

        gl.bindVertexArray(null);

        // -- Render
        
        var orientation = [0.0, 0.0, 0.0];

        requestAnimationFrame(render);

        function yawPitchRoll(yaw, pitch, roll) {

            var cosYaw = Math.cos(yaw);
            var sinYaw = Math.sin(yaw);
            var cosPitch = Math.cos(pitch);
            var sinPitch = Math.sin(pitch);
            var cosRoll = Math.cos(roll);
            var sinRoll = Math.sin(roll);

            return [
                cosYaw * cosPitch,
                cosYaw * sinPitch * sinRoll - sinYaw * cosRoll,
                cosYaw * sinPitch * cosRoll + sinYaw * sinRoll,
                0.0,
                sinYaw * cosPitch,
                sinYaw * sinPitch * sinRoll + cosYaw * cosRoll,
                sinYaw * sinPitch * cosRoll - cosYaw * sinRoll,
                0.0,
                -sinPitch,
                cosPitch * sinRoll,
                cosPitch * cosRoll,
                0.0,
                0.0, 0.0, 0.0, 1.0
            ];
        }

        function render() {
            orientation[0] += 0.020; // yaw
            orientation[1] += 0.010; // pitch
            orientation[2] += 0.005; // roll

            var yawMatrix = new Float32Array(yawPitchRoll(orientation[0], 0.0, 0.0));
            var pitchMatrix = new Float32Array(yawPitchRoll(0.0, orientation[1], 0.0));
            var rollMatrix = new Float32Array(yawPitchRoll(0.0, 0.0, orientation[2]));
            var yawPitchRollMatrix = new Float32Array(yawPitchRoll(orientation[0], orientation[1], orientation[2]));
            var matrices = [yawMatrix, pitchMatrix, rollMatrix, yawPitchRollMatrix];

            // Clear color buffer
            gl.clearColor(0.0, 0.0, 0.0, 1.0);
            gl.clear(gl.COLOR_BUFFER_BIT);

            // Bind program
            gl.useProgram(program);

            gl.uniform1i(uniformDiffuseLocation, 0);

            gl.activeTexture(gl.TEXTURE0);
            gl.bindTexture(gl.TEXTURE_3D, texture);

            gl.bindVertexArray(vertexArray);

            for (var i = 0; i < Corners.MAX; ++i) {
                gl.viewport(viewport[i].x, viewport[i].y, viewport[i].z, viewport[i].w);
                gl.uniformMatrix4fv(uniformTextureMatrixLocation, false, matrices[i]);
                gl.drawArraysInstanced(gl.TRIANGLES, 0, 6, 1);
            }

            requestAnimationFrame(render);
        }
    })();
    </script>
    <div id="highlightedLines"  style="display: none">#L132-L170</div>

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